This invention relates to improved flame retardants. In particular, this invention relates to water-soluble flame retardants useful for imparting flame retardance to cellulosic materials.
Cellulosic materials such as paper, fiberboard, straw, wood and textiles, such as cotton and wool, are highly useful materials whose utility is increased when their natural characteristic of being flammable is diminished. Thus, it is well recognized that the imparting of fire resistant properties to these otherwise highly flammable cellulosic materials increases the usefulness of the treated material.
Usually it is not practicable and sometimes it is not possible to make these flammable materials completely fire resistant or self-extinguishing. However, it is desirable to provide such materials with sufficient fire retardant properties to delay appreciably the propagation of the flame. It is also most desirable to prevent "afterglow;" that is, to prevent the material from continuing to smolder or burn at a very slow rate after the flame itself is extinguished. If afterglow occurs, the flame could break out again, or the material could be consumed or partially consumed because of the afterglow.
In teating these cellulosic materials to render them fire retardant, it is especially important that the treating method or additives do not impair the desirable natural characteristics and properties of the treated material, such as, its strength, flexibility, resistance to abrasion, color and the like. Also, any flame retardant additives or treating procedure should produce a uniform result so that the material treated does not have its properties adversely effected in spots or localized areas and, of course, the fire retardant characteristics should be uniform. The procedure or method for treating the material must be simple and easy to utilize with conventional equipment, inasmuch as the treated materials are almost always ordinary products of commerce, so that practical and inexpensive procedures are indicated.
In treating cellulosic materials with flame retardants, it is necessary that the treatment not add disadvantageous properties to the cellulosic material. One of the undesired results of treating cellulosic materials with flame retardants has been to discolor or darken the treated cellulosic product Also, certain flame retardant additives can diminish the strength of the cellulosic material to which they are applied.
Certain of the methods for flame treating cellulose materials require the use of an organic solvent, which is expensive and difficult to use and can adversely affect the flexibility of the cellulosic material. In this regard, U.S. Pat. No. 3,243,391 teaches the use of an isopropanol solution.
Also, British Patent No. 688,372 teaches the use of a partially polymerized brominated triallyl phosphate in an organic solvent to treat cotton for flame retardance.
Water-soluble, inorganic flame retardants have been in use for some time to impart flame retardance to normally flammable materials. Tbese water-soluble compounds include salts of sulfuric, phosphoric, hydrochloric and hydrobromic acid. Particular usefulness has been found for the ammonium salts including ammonium sulfate, ammonium phosphate, ammonium chloride and ammonium bromide. While these compounds can be used alone, it also has been established that mixtures of these water-soluble flame retardants with borax have functional advantages. These materials are advantageous since they can be conveniently applied to the normally flammable material by such known procedures as spraying, dipping and brushing. Yet, these flame retardant additives have not been totally satisfactory.
U.S. Pat. Nos. 3,671,376 and 3,834,937 refer to ammonium bromide and ammonium chloride as conventional flame retarding agents for wool and paper. U.S. Pat. No. 2,986,478 discloses the making of flame-proofed, water resistant paper with various water-soluble, flame-proofing salts including ammonium chloride by dissolving it in the aqueous phase of rosin-wax particle suspensions.
Kirk-Othmer, Encyclopedia of Chemical Technology, Volume 10, page 424 in Table 1 lists water-soluble flame retardants for textiles. Included in this table is ammonium bromide as the only flame retardant stated to be used as a 100% composition. This treatise on page 382 of Volume 10 highlights bromine compounds as having inherent properties that make them excellent flame retardants. In comparison to chlorine compounds, bromine compounds are about twice as effective as chlorine compounds having the same halogen content on a weight basis.
Yet, the use of ammonium bromide as a fire retardant has not been as commonas it could be due to various factors including the corrosiveness of the product. Also, while ammonium bromide has excellent fire resistance properties, its usefulness would be improved with the increase in the effectiveness of the application of the composition, which would decrease the amount of brominated material in contact with the metallic surface of the equipment used for the application of flame retardant to the cellulosic material.
Accordingly, it is an object of the present invention to devise new water-soluble flame retardant compositions of matter.
Another object of the present invention is to devise new flame retardants for cellulosic materials.
Still another object of the present invention is the preparation of paper products having improved flame retardance.
It is another object of the present invention to improve the effectiveness of the use of ammonium bromide.
Other objects of the present invention will become apparent from the ensuing description.